J. Am. Chem. SOC.1984,106,1291-7292
7291
Figure 4. Unit cell packing as viewed along the b axis.
Mossbauer [isomer shift = 1.59 f 0.03;quadrupole splitting (QS) UC13+cations,25and hydrated UOz(N03)2,26differs from those = 3.93 f 0.06 mm s-l] QS value, an LC-Sn-C angle of 160' can usually encountered with metal cations (e.g., K+),27hydrogenbe c a l c ~ l a t e d . ~ ~ bonded molecules (e.g., malononitrile),28or cation-coordinated water (e.g., Mn(N03)2-6H20)29 in that two aga units are replaced Acknowledgment. Our work is supported by the Office of Naval with gga units which allows two Sn-OH2 groups to approach Research (to J.J.Z.). We thank M & T Chemicals, Inc., for the opposite sides of the ring to interact each with four ether oxygens donation of organotin starting materials. Purchase of the Uni(see stereoview in Figure 3). versity of Delaware X-ray diffractometer was supported by a grant Each of the two crystallographically independent tin atoms lying from the National Science Foundation. We thank Dr. R. Harlow at a badly distorted Oh site [LC-Sn-C = 154.4 (2)', 153.2 (Z)'] at the E. I. du Pont de Nemours and Co. for help with recording is coordinated to a water molecule trans to a p-C1 atom of the the low-temperature data set. central Sn2CIzring. Such C1-bridged Sn2C12systems are found in [CgH8]+[(CH3),SnCl3]-(LC-Sn-C = 152.2"),3O bis(dimethy1tin Supplementary Material Available: A listing of atomic coordichloride-2,6-dimethylpyridineN-oxide) ( 145.3°),31[(CH3)2dinates and temperature factors (Table lS), bond lengths (Table SnC12.0=CC2(C6H5)2]2 ( 142.2°),32 and (CH3),SnC12 itself 2S), bond angles (Table 3S), anisotropic temperature factors ( 1 2 3 ~ ' ) . ~ ~Of3 ~the ~ five known examples, our p-C1- -Sn distance (Table 4S), hydrogen coordinates (Table 5S),and observed and is shortest. calculated structure factors (Table 7 s ) (18 pages). Ordering Although crown ether complexes of tin(I1) salt^,^^,^^ triinformation is given on any current masthead page. and phenyltin(I1) alkali-metal derivative^,^^ and organotin( IV) halides and pseudo halide^^^^^ have been prepared, (43) Sham, T. K.; Bancroft, G. M. Inorg. Chem. 1975, 14, 2281. the only structural determination available shows Oh, cis(H20)2SnC14units hydrogen bonded to uncoordinated water and ether oxygen atoms in Sn(OH2)2C14-18-crown-6~2H20~CHC13.41 Preparations of the title compound from methanol (mp 119-123 "C)@and isopropyl ether (mp 98-101 0C)42give different melting points from our product (mp 132-138 "C) from chloroform, Rate-Determining General-Base Catalysis in an Obligate recrystallized from methylene chloride. From the tin-1 19m le- Oxidation of a Dihydropyridine (25) Bombieri, G.; DePaoli, G.; Imrnirzi, A. J . Inorg. Nucl. Chem. 1978, 40, 1889. (26) Bombieri, G.; DePaoli, G.; Imrnirzi, A. J . Inorg. Nucl. Chem. 1978, 40, 799. (27) Dunitz, J. D.; Dobler, M.; Seiler, P.; Phizackerley, R. P. Acta Crustallogr., Sect. B 1974, B30, 2733. (28) Kaufmann, R.; Knochel, A,; Kopf, J.; Oehler, J.; Rudolph, G. Chem. Ber. 1977, 110, 2249. (29) Vance, T. B.; Holt, E. M.; Varie, D. L.; Holt, S . L. Acta Crystallogr., Sect. B 1980, 836, 153. (30) Buttenshaw, A. J.; Duchene, M.; Webster, M. J. Chem. SOC.,Dalton Trans. 1975, 2230. (31) Ng, S.-W.; Barnes, C. L.; van der Helm, D.; Zuckerman, J. J. Organometallics 1983, 2, 600. (32) Ng, S.-W.; Barnes, C. L.; Hossain, M. B.; van der Helm, D.; Zuckerman, J. J.; Kumar Das, V. G. J . Am. Chem. SOC.1982, 104, 5359. (33) Davies, A. G.; Milledge, H. J.; Puxley, D. C.; Smith, P. J. J . Chem. SOC.A 1970, 2862. (34) The two central, six-coordinated diphenyltin(1V) dichloride molecules in that tetrameric chain structure form a CI-bridged Sn,C1, system (Bokii, N. G.; Struchkov, Yu.T.; Prokofev, A. K. J . Sfruct. Chem. (Engl. Transl.) 1972,13,619) with LC-Sn-C = 125.5' (Greene, T.;Bryan, R. F. J . Chem. SOC.A 1971, 2549). (35) Herber, R. H.; Smelkinson, A. E. Inorg. Chem. 1978, 17, 1023. (36) Herber, R. H.; Carrasquillo, G. Inorg. Chem. 1981, 20, 3693. (37) Bullard, W. R.; Taylor, M. J. Aust. J . Chem. 1981, 34, 1337. (38) Gur'yanova, E. N.; Ganyushin, L. A,; Romm, I. P.; Shcherbakova, E. S.; Movsumzade, M. J . Gen. Chem. USSR (Engl. Transl.) 1981,51, 356. (39) Cusak, P. A.; Patel, B. N.; Smith, P. J. Inorg. Chim. Acta 1983, 76, L21. (40) Smith, P. J.; Patel, B. N. J . Organornet. Chem. 1983, 243, C73. (41) Cusack, P. A.; Patel, B. N.; Smith, P. J.; Allen, D. W., Nowell, I. W. J. Chem. SOC.,Dalton Trans. 1984, 1239. (42) Russo, U.; Cassol, A,; Silvestri, A. J . Organornet. Chem. 1984, 260, 69.
Ashoke Sinha and Thomas C. Bruice* Department of Chemistry, University of California at Santa Barbara, Santa Barbara, California 93106 Received July 30, 1984 In the main, reduction reactions by dihydropyridines involve hydride transfer. Many proposals that the overall two-electron reductions of oxidants proceed by an initial electron transfer from dihydropyridine to oxidant have recently been shown to be faulted by the experimental methods employed to study these reactions.] There are, of course, examples of one-electron transfer from dihydropyridine~.~-~ Experimental evidence has been offered in support of the following mechanism (eq 1) for the ferricyanide r e a ~ t i o n .The ~ rate-determining step, shown here in the ferricyanide oxidation of N-methylacridan (MH,), is the generalbase-catalyzed proton ionization ( k 2 ) .
(1) Powell, M. F.; Bruice, T. C. J. Am. Chem. SOC.1983,105,7139-7149. Powell, M. F.; Bruice, T. C. J . Am. Chem. SOC.1982, 104, 5834-5836. (2) Schellenberg, K. A,; Hellerman, L. J . Eiol. Chem. 1958, 231, 547. (3) Carlson, B. W.; Miller, L. L. J . Am. Chem. Soc. 1983,105,7453-7454. (4) Powell, M. F.; Wu, J. C.; Bruice, T. C. J . Am. Chem. SOC.1984, 106, 3850. (5) Okamoto, T.;Ohno, A.; Oka, S . J . Chem. SOC.,Chem. Commun. 1977, 181. Okarnoto, T.; Ohno, A.; Oka, S . Bull. Chem. SOC.Jpn. 1980, 53, 330.
0002-1863/84/1506-7291$01.50/00 1984 American Chemical Society
7292 J. Am. Chem. SOC.,Vol. 106, No. 23, 1984
Communications to the Editor
io 0
r
766
740
6.0
bcoNHZ not rate determining
1
R
+I
R
--
L
The oxidation of MH2 (4.7 X 10" M) has been studied under a nitrogen atmosphere in 20230 acetonitrile-water (v/v) solvent at 30 f 0.1 O C by following the increase in A359with time under the pseudo-first-order conditions of [ Fe(CN)63-] >> [MH,] > k, [buffer base] and the general-base-catalyzed dissociation of the carbon acid MH2+. is rate controlling. The final piece of evidence required to substantiate the mechanism of eq 1 for an obligate le- oxidation of a dihydropyridine has been put in place.
-
Acknowledgment. This work was supported by a grant from the National Science Foundation. Registry No. MH2, 4217-54-3; deuterium, 7782-39-0.
( 6 ) Bell, R. P. "The Proton in Chemistry"; Cornell University Press: Ithaca, New York, 1973; p 200.
